1. Field of the Invention
This invention relates generally to semiconductor laser device, and more particularly, to devices which achieve high-power operation due to full-aperture emission from a broad emitting facet while suppressing lateral amplified spontaneous emissions.
2. Brief Description of the Prior Art
Current laser applications are requiring large linear power densities which have been difficult to achieve heretofore. The output power of semiconductor laser devices is limited by catastrophic optical degradation of the laser facets which occurs at a given facet output power density. In order to increase the total maximum power it is therefore necessary to enlarge the emitter's surface area by increasing the width of the emitting facet. Generally, the width may only be increased until it approximately equals the cavity length at which time joule heating and competing radiative pathways being to impair the laser output.
Previous solutions to the output power limitations have included mechanical stacking and multielement or laser array schemes. Alternatively, prior attempts to reduce the competing radiative pathways, or amplified spontaneous emission, have sought to spoil the cavity in the lateral direction by chemical etching, regrowth, or proton bombardment. While these alternative solutions are successful, they require complex processing and stringent quality control and some of the processes are inherently damaging to the crystal.
An alternate method for decreasing the amplified spontaneous emission relies upon a nonplanar active region grown epitaxially upon a corrugated substrate. This method was proposed by M. E. Givens, et. al., of the University of Illinois, Applied Physics Letters, 53(13), p. 1159, September 1988, however this laser device failed to fill more than 40% of the aperture with the lasing occurring only at the steep steps between the planar regions due to an index-guiding mechanism. Additionally, the planar regions of the semiconductor laser disclosed by Givens, et. al., were only 5-.mu.m wide so as to further limit the percentage of the aperture filled and the thus restrict the laser's power.